1. Field of the Invention
This invention relates to a fluid pressure device such as oil hydraulic and hydraulic device, and more particularly to a pulsation damping or absorbing device incorporating therein an inner cylinder having freely movable valve members.
A pulsation damping device comprising such an inner cylinder is provided, at the both axial ends of its cylindrical body proper, with an inlet ring and an outlet ring, a gas chamber, a resilient annular diaphragm and an inner cylinder formed with a plurality of communicating holes, both being concentric one with the other. The inside of the inner cylinder constitutes the passage for pressurized fluid and the device prevents an outbreak of shock wave and/or pulsation in the fluid flow.
In this kind of pulsation damping device as mentioned, however, there is a fear that the resilient diaphragm is liable to be damaged by being forced into communicating holes when it is urged to tightly contact the inner cylinder due to the change in the fluid pressure.
In view of this fact, an effort has been made in the prior art device of this type, as shown in FIG. 5, to provide one or more leaf springs 5 and a resilient valve shoe(s) 6 stacked with each other, between a resilient diaphragm 2 and an inner cylinder 3 and at the place where they can cover communicating holes 4, and these two parts are connected to the inner cylinder by a pin 7 so as to permit slidable movement along the axis of the pin 7 but with its stroke of movement smaller than the amount of stroke caused by elastic deformation of the leaf spring 5 in the direction of the axis of the pin.
According to the prior art device as mentioned above, when the leaf spring 5 is urged by the resilient diaphragm 2 and closes the communicating holes 4, that is, under the condition as shown by a dash line in FIG. 5, if the fluid pressure within the inner cylinder 3 increases, the fluid would flow through the communicating holes 4 in the direction shown by the arrow mark A4 and apply a pressure to the resilient diaphragm 2 and abruptly removes the resilient diaphragm 2 away from the pin 7 and the resilient valve shoe 6 stacked thereto.
The pin 7 and the resilient valve shoe 6 which having suddenly been released from the urging force of the resilient diaphragm 2 will rapidly move, under the resilient force of the leaf spring 5 as well as the fluid force in the direction shown by the arrow mark A4, to the direction shown by the other arrow mark B4 followed by severe impinging of the stopper 8 of the pin 7 upon the inner cylinder 3 accompanying sudden stoppage of the pin 7.
Accordingly, some parts of the device such as the head 7a of the pin 7, the stopper 8 and the resilient valve shoe 6 are apt to be damaged under such impact stress.